1. Field of the Invention
The present invention relates to an image display device, and more particularly, to a method and apparatus for adaptively converting a frame rate based on a motion vector, and a display device with an adaptive frame rate conversion function.
2. Description of the Related Art
Television (TV) signals received using an interface method have a 60-Hz frame rate in National Television Standards Committee (NTSC) systems, and a 50-Hz frame rate in Phase Alternating Line (PAL) systems. However, since TV signals are received at 24 Hz in terms of movies, a movie frame rate is converted generally using 3:2 or 2:2 pull-down, and the frames are displayed. This image conversion technology is called a Frame Rate Conversion (FRC) method.
FIGS. 1A and 1B are diagrams for describing a related art FRC method.
FIG. 1A illustrates frames o1 having one odd field and frames e1 having one even field. In frames o1, a ball is located in the lower left corner, and in frames e1, the ball is located in the upper right corner. FIG. 1B illustrates a result obtained by applying 3:2 or 2:2 pull-down to the frames o1 and e1. Five frames P1 through P1 illustrated in FIG. 1B are implemented using the two image signals of the frames o1 and e1 illustrated in FIG. 1A. In this process, if an image signal having a 24-Hz frame rate is received, a first frame is displayed twice or three times, and a second frame is displayed twice, the two image signals are not continuous as illustrated in FIG. 1A. Thus, for the related art FRC method, it is required to generate continuous frames P2 through P4 using the two image signals of the frames o1 and e1. The technology of generating intermediate frames using two discontinuous image signals is called frame interpolation technology.
According to the related art FRC method, interpolation images are generated by weighting and adding the two frames o1 and e1. In order to generate the interpolation images, a display device obtains a motion vector corresponding to a dominant motion of an interpolation image and extracts a dominant movement direction from the motion vector. A weight used to generate another interpolation image is changed based on the dominant movement direction.
In all display devices up-converting a frame rate using a motion prediction and motion compensation method, artifacts due to a motion compensation error are generated in an edge portion of each image. These artifacts are caused by a motion error of an uncovered area, which is generated in a previous frame or field or a subsequent frame or field. In addition, if a local motion occurs inside a boundary of a panning image due to the movement of a camera or an image in which a dominant motion significantly occurs, an error occurs even in a compensated motion vector.
FIG. 2 illustrates artifacts generated when the related art FRC method is applied. The artifacts are generated in portions represented by dotted lines among the images illustrated in FIG. 2. Thus, related art display devices hide a portion in which an artifact is generated, by setting an active region. In this case, a viewer cannot help but view a screen that is a little bit smaller than an actual screen, and if a circumference portion of an image exists in the image, a motion compensation error still occurs.
Thus, an interpolation image generation method of canceling an artifact generated in an FRC process is required.
In addition, a display device for displaying a received image in its original size without setting an active region of the received image is required.